1. Field of the Invention
This invention relates generally to automatic shutoff valves controlled by the fluid level in a container.
2. Prior Art
When filling a container with a fluid dispensing device, such as a water gun, an operator must closely monitor the fluid level. The valve on the dispensing device, such as a trigger, must be manually kept open for a prolonged period, and manually closed when the desired fluid level is reached. This method is time consuming when filling a large container, and tedious when repeatedly filling multiple containers.
Numerous automatic shutoff valves are known for shutting off flow when a predetermined fluid level is reached in a container being filled. They are particularly useful for automatically filling the cells of a lead-acid battery to a predetermined level. However, they are relatively complicated and expensive to produce.
A simpler automatic shutoff valve is shown in U.S. Pat. No. 4,556,093 to Jones, and is arranged inside a dispensing device. It includes a movable tube connected to the downstream end of a constricted venturi, which directs a jet of fluid along the inside wall of the tube. A ball positioned upstream of the venturi is connected to the movable tube by a wire. The ball is kept away from the venturi by a spring. The venturi causes fluid flowing there through to substantially increase in velocity and decrease in pressure relative to the liquid at the upstream end thereof. Before the fluid level in the container reaches the lower end of the dispensing device, the pressures between the upstream and downstream ends of the venturi are equalized by outside air flowing into the movable tube from the lower end of the dispensing device. When the fluid level in the container reaches the lower end of the dispensing device, air can no longer enter the movable tube to equalize the pressure. The low pressure of the fluid jet draws the movable tube away from the venturi. The spring loaded ball is pulled against the venturi, and fluid flow is shut off. However, the movable tube cannot slide smoothly because it is only guided at the upstream end by the venturi. The downstream end would wobble in the jet and cause the upstream end to stick to the venturi. The valve is relatively long, so that it can fit a limited variety of dispensing devices. Also, the single venturi limits flow rate to a relatively low level.